Management Impacts On Sorghum Silage Ruminal Digestibility



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The impetus for sorghum (Sorghum bicolor L.) silage to replace corn silage in beef cattle and dairy rations has increased due to sorghum’s ability to grow well under water-limited conditions. Two experiments were conducted to evaluate the effects of maturity, mechanical processing, ensiling duration, and hybrid on in situ ruminal digestibility. In Exp. 1, three ruminally cannulated beef steers (BW = 463 ± 15 kg) were used to evaluate the effect of maturity stage, mechanical processing, and ensiling duration on in situ digestibility of forage sorghum silage. A brown midrib (BMR) forage sorghum (Alta Seed AF7401) was harvested at soft dough (SD) and hard dough (HD). Within each maturity stage, sorghum kernels were processed (C) using a chipper shredder or left unprocessed (W), and were subjected to 0, 30, 60, or 120 d of ensiling. In Exp. 2, three ruminally cannulated steers (BW = 570 ± 17.9 kg) were used to evaluate sorghum hybrids and ensiling duration on in situ silage digestibility. A BMR forage sorghum (Alta Seed AF7401), conventional forage sorghum (Sorghum Partners NK300), and a grain sorghum (Sorghum Partners SP33S40) were ensiled for 0 or 60 d, which was the optimal ensiling duration for Exp. 1. In Exp. 1, kernel processing increased (P < 0.01) the effective ruminal degradability (ERD) of DM, OM, CP, and starch in SD sorghum silage and increased the ERD of starch in HD silage. Ensiling duration affected (P < 0.01) the ERD of all in situ disappearance variables for SD silage, except (P = 0.40) the ERD of
starch. The ERD of in situ variables in HD silage was affected (P < 0.01) by ensiling duration. In situ ERD of DM, OM, CP, and starch was different (P < 0.01) between hybrid type. Ensiling affected (P < 0.01) the ERD of CP and starch, with no differences observed (P ≥ 0.32) in the ERD of DM and OM. Kernel processing and increased ensiling duration improved in situ digestibility of both early and late matured sorghum silage. Hybrid type may influence silage digestibility, thus livestock producers should consider hybrid selection to maximize ration digestibility.



Sorghum Silage Digestibility, Silage Management, Ensiling, Silage Processing, Silage Maturity


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